Accurate classification and treatment of speech disorders requires an understanding of the development of vocal communication in early life. Using songbirds, whose vocal development bears relevant similarities to that of humans, the proposed research will provide experimental tests of an "active" model of vocal learning. This model expands upon prior models by considering recent evidence that birds alter memorized song models during the sensorimotor phase of learning. In two experiments, swamp sparrows (Melospiza georgiana) will be hand-reared in the laboratory, and will be tutored with songs that are modified to be species-atypical in rate or rhythmic consistency. Sounds produced by the young birds will be monitored throughout development. In cases where the final (crystallized) songs differ from the tutored originals, the revised model predicts that birds will memorize atypical songs accurately, but modify these representations later in development to optimize performance. These experiments, and a third on the responses of adult birds to song playback, will yield insights into the distinction between perception and production in vocal learning, the timing of individual modifications, and the mechanistic origins of vocal anomalies.